Field of the Invention
The present invention relates to a semiconductor structure, and in particular relates to a protection layer for a passive device of a semiconductor structure.
Description of the Related Art
For a conventional flip chip package, one criterion of inductors is low resistance, so that a high quality factor (Q factor) can be achieved. The quality factor (Q factor) of an inductor is the ratio of its inductive reactance to its resistance at a given frequency, and is a measure of its efficiency. The higher the Q factor of the inductor, the closer it approaches the behavior of an ideal, lossless inductor.
The conventional package fabrication process usually uses nickel (Ni)/gold (Au) layers as protection layers for the inductor. The Ni/Au protection layer can prevent the inductor from oxidation. However, the Ni/Au protection layer will cause the skin effect in the inductor. Also, the Ni/Au protection layer usually has a thick thickness. The thick Ni/Au protection layer on a surface of the inductor will degrade the Q factor and resistance of the inductor.
Thus, a novel inductor with an increased Q factor is desirable.